Railway-traffic-controlling system



Feb. 25, 1930. H. P. OBER RAILWAY TRAFFIC CONTROLLING SYSTEM Filed July25, 1927 vm mP W M f;

l NTOR o M ATTORNEY Patented Feb; 25, 19 30 I M f .U STA .EERMON 3.013123; or ROCHESTER, new YORK, Assmnoa mo GENERAL RAI WAY r SIGNALooivri anv, on nocnnsrna, NEW roan w 7 RAILWAY-r1am?n1ocoiI RQLtINGsYsTnM Applieati on' fil ed J'u1y 2'5 1927. Serial No.-208,249.

This inventionrelates to absolute-permis s'ive-block signaling systems,and more particularly to a light signaling system of this type in which,dire'ctcurrent track circuits 5-are employed. f e i y' 3 As'is well.knownfby those skilled in the art of A. RB. signaling, there is employedin vsuch signaling. a directional stick relay, 'which it once picked upis stuck up so long I as the associated home relay remains de-energized,and serves to permit the next signal inthe rear to goto caution eventhough the associated homerelay of such stickrelayis d e-energized.,:For this reason, -"it'is importantto avoid this directional stickrelaypick- 1 mg up momentarily at a time whenthe home relay is down andwhentraffic conditions are such that the stick relay should not beenergized. In A. P. B systemsit is quite comnoon to employ cuttracksections resulting in a plurality of track'circuits perblock, andit has been experienced where direct current I track circuits are usedthat a home relay controlled through the front contact of two suc- Icessive track relays, that this home relay is apt-to pick up momentarilywhen ashort train passes from one track circuit ontofthe next track.circuit; this because the dropping I of the energized 'trackrelay isconsiderably ,30 delayed inthat among other things it is short circuitedwhen de-energize'd by aI-passing -t1ain;whereas' the track relay of thesection just occupied bysuch moving train picks-up very quickly, and insome cases has actually been known to pick up before the track relay ofthe section, in advance dropped; so that the circuit for the'home relay;controlled through front contacts of such track relays picked up. 'Asisreadily appreciated by one momentarily picking up of the home relay maycause false energization of the directional stick relay." I 1 With theforegoing and'othe'r important considerationsin mind, it is proposed inthe? cordance' with the present invention to avoid the home relaycontrolled by front contacts of the track :relays of two successive;track sections lbei'ng momentarily "picked up, I even successive tracksections."

of the adjacent ends of two track sections in series would in that casebe momentarily a passlng slding containing a track switch skilledin theart 'otAnP. 'B. signaling, such though there is a very short trainmoving from onetrack section upon thenext, track Generally speaking, itis proposed to stagger the insulated joints between two successive tracksections, and

section at a high speed.

to provide suitable means whereby the track batteries of both of thejtwosuccessive track sections are cut oil? of their respective track relaysso long as there is a wheel and axle between the insulating vj oints ofthe staggered junction of the two successive track sections. Morespecifically, it is proposed to provide gered joints that this relay isenergized when a wheel and axle bridgesirails between the staggeredoints of'the'junction between two Otherobjects; purposes andcharacteristic features ofthe invention will appear'a's the. t

description thereof progresses.

In describing the invention in detail" reference will be made to theaccompanying drawings in which:

tem of the A. P. B; type employing direct Fig. l-shows apor'tion ofalightsignal sys- I v i a relay in such a manner between these stag.-'

current track circuits and embodying the present invention. i

Fig. 2 shows a modified form o'f the inven tion in which the junctionsof two successive track sections employ a track-battery adja-U cent thejunctions in one track section and a 1 track relay adjacent thejunctions in the other track section; and Fig. 3 shows still anotherapplication of the invention in which each TS. The portion of the,absolute perinissi'veblock signaling system shown includes the enteringstop-and-stay signal 1,]the -starting structm'e of F 119.] .Refcrring toFig, .1

stop-and-stay signal Qand two 'intermedlate permissive signals 3 and arespectively. It may be pointed out here that thestop-andstay signal 2is distinguishable from any one of the permissive signals 1, 3 and 4,-inthat the stop-and-stay signal has almarker'light e M directly in linewith thegreen yellow and M of the permissive signals 3 and 4 are offsetwith respect to the light signal units 5 thereof. v V

In orderto; simplify the description ofthe present invention-the controlcircuits and relays for the permissive signal 3 only have heen shown.The block between the signals 19 l' and 3 the ends of which are definedby insulating joints 9,'has been shown divided into two track sectionsinsulated from each other by insulating joints 5 and 6, although inpractice more than two out sections per block may be employed, ifdesired. The first of these track rsections considering east bound trainmovement includes a track battery 7 and a ,track relay 2T, and theothertrack section ,includesratrack-battery 8 and a track relay 30. 351.sItis noted that the home relay 31-1 is ensergized through-the followingcircuit :-ber-rgi-nning at the terminal B of-a suitable bat- Qtery,contactlO ofthe track relay 2T, wire .11, contactl2-of. the trackrelay3T, wire 13,

winding of the homerelay3H, to the common return iwire C connected tothe other terminal ,ofthe' battery containing terminal B. This homerelay 31-1 is a polarized relay and in .practice is energized in thenormal orrr'everse .430v direction depending upon whet-herthe-signal inadvance ofthe signal 3 is at stop or at pro ceed, that is, the terminalB may be either ..p'ositive or negative.

This relay 3H, by its front contact 15, di

i1 rectly controls the energization of the slow dropping polechangerrelay SPC. The pole changerrelay 3PC is preferably made slow to drop fortwo reasons, namely, first, to permitthe picking. up of the stick relay3S in a o manner as more thoroughly pointed out hereinafter and, secondto avoid flashing of the red light R of the signal 3 due to momentaryde-energization of the relay 31 6, while the polar relay 3H is changedfrom its J normal energized condition to its reverse-em ergizedcondition; The manner in which the directional stick relay 3S is pickedup if :the homerelay 3H is-momentarily energized, ...and the manner inwhich it is controlled, is

.50 more readily pointed out in connection with the operation ofthesystem. It shouldbe noted that the insulating jointsfi and 6separating the two track sections inquestion are staggered, and that ifthere is a wheel and tangle between these staggered insulatingjointsthat the relay-X will be picked up, becauseacircuitincluding thewinding of this relay Xand the two batteries 7 and S in seriesis/completed. Further, it will be noted that .ivhenthe relay is in itsenergized condition -thattheitrack battery? is cut off of its trackcsect-ion by-reason o'fopening of contact 17 of the relay X, -andthat-thetraGkbattery 3 is cut off of its track; section by reason ofthen opening-Qt contact 18.

Operation Fig. 1.Let us first consider'the movement of a train fromright to left by the signal 3, and let us observe how the stick relay 3Sis picked up in order to permit another train to follow the train inquestion. When the west bound train, moving from right to left, passesthesignal 3, it treads upon the track circuit containing track relay 3Tand effects rde-energization ofitllis relay 3T, and dropping ofrelay'3T'in turn effects de-energization of the home relay 3H, and thedropping of which in turn tie-energizes the pole changer relay 3P0.Since, however, a considerable delay in the dropping of the contacts ofthe pole changer relay 3P0 is experienced,

becansethis relayBPCis slow droppin a W a: pick up circuit for the stickrelay 35a is tempora-rily established which may be traced as follows:-beginning at the terminal B, back contact 20 of the track relay 3T,wire 21, front contact 22 of the poleI changer relay 3P0,

'wires 23 and 24, winding of the directional taining terminal B.

7 Since the home relay 3H drops quicker than the pole changer relay 3PCthe following stick circuit is completed before thevpick up circuit usttraced is broken :Vbeg-inning at theterminal'B, front stick contact 26of the stick relay 3S, wires 27 and 28, back contact 29 of the homerelay 3H, wires 30' and 24, winding of the stick relay 38, to the commonreturn wire C. After another short interval oftime the relay 3P6 willhave assumed its .1 de-energized condition and thereby will havecompleted the following additional stick circuit for the relay 35:beginning at the terminal B. contact 26 of the stick relay 3S, Wires 27and 32, back contact 33 of the pole changer no;

relay 31 C, wires 34 and 24:, winding ofthe stick relay 38, to thecommon wire C.

It is thus noted that the movement of a train from right to left bythesignal 3 causes the stick relay 3Sto'be picked up and stuck energizedfor train lengths andtrain' speeds ordinarily employed in practice andthereby lie; maintains the relay 3S stuck up. l/Vhen this train movesoff of thelast section inthis block the track-relays 3T and 2T will bothbeup thus causing the home relayBHto again be BDGTgIZGClZLIlCl in turncausing the -pole changer relay 3PC to be energized and a rather highspeed, assuming that the. relay the stick relay 3S tobe de energized,for obvlous reasons. Had the train in question been a very short tramand-had it moved at forming an essential part of the present inventionhad not been used in this) system,

1 the movement of the train from the track sec- 1 tion containing trackrelay3'l: upon the track section containing-track re y 23 m ght ave i[allowed the trackrelay Tto be pickedup before the track relayQTdroppedand thereby-might have momentarily picked up the} home relay 3H. r 'lnthis connection it is do "sired to point out that a direct current trackrelay when shuntedby the presence of a train quick in picking-up. Theniomentary ener in turn would prevent another train follow gization ofthe relay 3H for reasons just j firnentioned 1n asystem" such as, shownwould.

permit dropping ofthe' stick relay 38,- which ing the train in question.This in itself is not a hazardousor'dangerous condition, but

is undesirable" in that it unnecessarily interferes with the'movement'ottraflic; f "-If thetra'in in questionhad been moving. 7

rings the protective relay X has been shown 7 fror'n'left to'right,under which condition of train movement the'stick relayj 38 would be itsde-energized condition, the momentary picking up and dropping of thehome-relay- "3H, in aisystern in which therelay Xofthe presentinventionis not employed, could have momentarily completed the pickupcircuit for the stick rieliyiS, and thereby caused this relaySS to bestuck up. This ialse plcking up of the stick -relay 3S would, o1 course,set -np a very dangerous condition'because 1t train with'respect to thetrain in question in the single track sect on connecting two passingsidings. Although trains moving towould permit the entrance of anopposing ward'e'ach other in alsin'gle track section-of an A. P. B.system" will in'a way" be protected by signalindications, these signalindi .cations merely-assure braking distance ahead of a moving train,and if two trains are moi l i'n g toward eaclrother double braking dis:

" that'the 1 quate.

tances is necessary to prevent collision, so signal protection afiorded1s nade- I Lu; snow see how the introduction cra "relay X avoids themomentary picking up of the'relay' 3H Let us consider the movement fof atrain from left to' right" between the 'sig'nals 1- and. 3 underwhichcondition of; train movement the 1 ."elays-SH; 3P6 and 38 will inpractice," all assume their tie-en 1 ergized condition, in the firstinstance this. fbeing due to the presence of the train on the trackcircuit containing the track relay,

2T. As this trainmoves from left to right the'moment itpasses by:tl 1einsulated joint '5 thelpr'otective relay X is energized through thefollowing circuit :'beginning atthe bat'-,,

tery 7 wires eiOand 41', windingof the relay X, wires t2and 43, trackbattery 8,

' throughthewheels and axles of the train in question back to thebattery 7. This enerr' gizationof' the protective relay X will effectraising of theicontacts 17 and 18 tiereby disconnecting the batteries 7and 8 from their respective track circuits. Although the operation ofthese contacts 17 and 18 will "not" :in any Way affect theene'rgizingcircuitof the relay X including these same batteries v7 and 8,.theiroperation to the raised position opens V the two track circuits- It"thus appears that so long as any part ofthe train occupies the" "tracksbetween insulating joints 5 and 6 that no track circuit current will beavailable-for energizing either of the track relays 2T. or 3'1, and thatfor this reason the home relay 8Hjwill notbe momentarily pickedup rel:

gardless of the length of the train in ques- 'tion or the speed at whichitmoves from; one

tracksection into another; in other woitls,

the applicant has solved the diiiiculty-lmretofore mentioned by going tothe root of the: trouble by avoiding'mornentary picking up of the homerelay 8H.

Structure Fag. '2.--II1 2 of the drawi applied to the junctions betweentwo .succes sive track sectionsat a signal location where the ad acentends of two track sections in clude a track, battery ".and a track relay5T, respectively. That is, it is the practice f in A; P. B. signaling.to arrangethetrack batteries and track relays of a track circuitin'such a way that the track relay which directly controls a signal inquestion is located near such signal: In the arrangement shown theinsulating joint-s 46 and 47 are staggered in the same way'as. thejoints '5 and 6 have been shown staggered in Fig 1 ofthe drawin gs;Also, in Fig. 2 "of'the'drawings the protective relayXwhen energizedopfensthe "track circuits for both'of the two adjacent f track sectionsby opening the contacts 48 and track circuits are opened so long ass.train bridges the portion ofthe railway track between the stagger jointsof the junctions of the track sections thereof. It will be noted I -thatin Fig. '2 ofthe. drawings there is only.

one battery, namely the battery 45, in the energiz ng circuit of theprotective relayfX joints of thejunctions of the two track sec-- tions;whereas two batteries, namely batteries 7 and 8, are contained in theenergizing circuitof therelay X ofFig. l underis imilarj '49 of therelay X. The usual limiting resistwhen there is a train between thestaggered material because therelay 'X willinpractice 'be designedsofaas-to function properlyifor --the number of batteries usedin itsenergiz :ing circuit and the voltage of these batteries. 1 In view ofthe:similarity between the apparatus at the junctions oftwo successivetrack circuits, shown in Figs. 1 and 2, it is deemed unnecessary tofurther discuss the application of theinvention asshownin Fig. 2 of thedrawings.

Structure F 3.In Fig. 3 of the drawings has been shownanarrangement:where the adjacent-ends oftwo track circuited sections of:an'A. 'P. B. system contain track relays 7T and 8T respectively. Inthearrangement shown irrFig. 3 .the insulatingjoints 53and=54havealsobeen staggered for reasons already mentioned in connectionwith Figsl and 2. By reason of the fact that-neither of theadj acentends ofthe-track sectionszshown in Fig. 8 of the drawings contain atrack battery it isnecessary to provide a separate battery forenergizing'the relay X while a passing-train occupiesithetrackmails-between the stagger'joints 53 and In thearrangementshownthereis con nected in series'with theprotective relay X a battery 55. It=isthus noted that if'there is:.a train present-between the staggeredinsulating joints 53 and 54, the presence of this train will causetheenergizing circuit for the relay 'X which includesthe battery 55 tobeccompleted; and it is furtherapparentthat therelay X so long asenergized will open 't-hetra'ck circuitsof the two, adjoining tracksections'bythe opening of contacts 56 and ;57,-respectively. Inother'wor'ds, in Fig. 3 of the drawings the protective relay Xisenergized so long as there is a train present on the track between thestaggered joints 53 -1and'54, and witlrthis protective relay X enopenedin'the same wavas those of the rangeinent shown in Figs. 1 and 2 of thedrawings, so'that no detailed description of --the operation of themodified form of inven- ItIOIl shown 2 in Fig. 3 of the drawings need.begiven. Although theinvention has been :shown zappliejdto asignalsystem employing 1 direct current track circuits it may be appliedto av'system employing alternating current 7 track scircuits,; if:desired.

Havingi thus 'sho'wnseveral specific embodigments-o'f Ethe :present;invention, and "havin g shown "rather specific circuit arrangementsi'tor accomplishing the desired result. it is desired :to E beunderstood that this has been "done iforrtheipurpose of simplifying thedesscriptiomof; the invention rather than illus- I tnatin'g?itsrscopeyorjthe specific "arrangement 'ipreterablyrem ployeid'inpr-acticing; the same; aandiitzisiiur thenideSireZdtodoexunderstolodthat engizedthe adjacent track circuits will be ":various changes,modifications and additions maybe-made tothe arrangements-shown in orderto adapt theinventionto theaparticular signaling problem encountered inpracticing the invention, all :without' departing from the spiritorscope ofthe invention or the idea of means 11nderlying-':thesame,gexcept as demanded by scopeof the' follo'wing claims.

that I claim is 1. In a railway signalingsystem, the com- L binationwith a railway'track' dividedinto sections by insulated joints;-.atrack'circuit of the usual :type including asource of energy, the trackrails of a sectionandaafltra'ck relay connected in series, for eachof-twosuc cessive track sections; and meansjforopening said two trackcircuits when a train passes the track between the staggeredinsulatedjoints separating the two adjacent track sections.

3. In arailwaysignaling system; the combination with arailway trackdividedjnto sections by insulated .j-ointsplaced in-staggered relation atrack circuit 1 of the usual type including a source-of energy,' thetrack rails of a section and'a track relay. connected in series, foreach of two successive-track-sections; and means includinga'protective-relay for opening said two track circuits when a trainoccupies that portioniof the track be-- tween the staggered insulatingjoints separatingsuch two adjacent track sections.

.4. In a railwaysignaling system of the absolute-permissive block1typein which. it is dangerous for a line relay tobe momentarily ienergizeddue to the' passage ofatrainythe combination with a railway trackdivided into sections by insulated jointsya-track circuit of theusualtypeincluding asonrce of energy, the track rails of a section andatrack vrelay connected in series,.foreach oftwojsuccessive tracksections"and means for opening the'two track circuits of the two. sucCGSSIVGSQCUOIIS :when a: trainpasses from-one track section into theother of said track sections whereby the line @relay controlled :by suchtrack circuits is not momentarily ener- ,gized combination with arailway itrack fliwzided into sections insulated joints placed in fstaggered, relation; a track circuit of the usual type including"'a-source of energy, the

track rails ofa section and a track relaycon- V nected inseries, foreachof -two successive track sections; and means for opening the twotrack circuitsfor the two successivesections when a train occupies thatportion of the track between staggered insulated joints separating suchtwo adjacent track sections. I l

6. "In a railway itig'naling system of the ab 7 solute-permissivebiocktype in which it: is

dangerous for a line relay to be momentarily energized due tothe passageof a train, the combination with a railway track divided into sectionsby insulated" joints placed in staggered relation',a track circuit ofthe usual type for each' of two successive vsecaxle withitswhe'elstooccupyone rail of" ea'chof two successive track sections, a track tionsincluding a sourceof energy and a track relay, andmeans lncludlng aprotective relay controlled in amanner to open said two track circuitswhen a train occuples that portion of the track between the staggeredinsulated joints separating said two-adjacent track sectiong; 1' ii 7 V,A v

7;; In a railway signal" system, the" combination with a railway trackdivided into blocks by-insulated joints, other insulated joints fordividing oneof'saidblocks into track sections which otherjoints arearranged in'staggered relation so as to perniita single circuitforeachsectionot said-one block each including theusual track battery and atrack relay, and a protective relay connected across the rails of the-'trac k' between 1 said staggered insulating joints,--and a' backcontact of sa1d protective relay connectedin one' of said trackcircuits. t

'8. In a railway signal systein, the cornbination with a railway trackdivided into blocks by insulatedjoints, other insulated joints fordividing one of sald blocks lnt'o track sections which other oints arearranged in staggered relation so as to permit a single aXle with itswheelsto occupy one rail of each of two successivetracksections, a track1 circuit for each section of said one block each V a track circuitincluding the usual track battery anda track relay, and a protectiverelay connected across the rails of the trackbe tween said staggeredinsulated o nts, and two back-contacts on said'protectlve relay onecontained in one of said track circuits 'and'the' other contained in theother of said 'trackcircuitsf 7, r v r GOT i dividing one of said blocksinto track sections relation so as to perniit a single axle with itswheelsto occupy'one railof'each oftwo suc 9. In a railway signal system,the combination with a railway trackdivided into blocks by insulated joints, other insulated joints for which other joints are arranged instaggered cessive track sections,:a track circuit foreach section ofsaid one block each including the I r usualtrack battery and a trackrelay-,"one of said track circuits being arranged to have its trackrelaylocated at the end adjacent said staggered joi nts and the other ofsaid track circuits being so arranged that its. track bat l tery is atthe Lend adjacent said staggered joints, a'protective relay connectedacross the rails of the track-between said staggered joints; and a backcontact of said protective we relay connected in one of said trackcircuits; I

10. In a railway signal system, the combiblocks byinsulated joints,othe'rinsulated joints for dividing one of said blocks into tracksections whlch other oints are arranged nation with a railway trackdivided into in staggered relation so as to permit'a single I r axlewithits wheels to occupy one rail of each of two successive track sections,atrack circuit for each section of said one block-each in"- cluding theusual track battery and a track ranged to have its track relay locatedat the end adjacent saidstaggered joints and the relay, one of saidtrack circuits being an other of said track circuits being so arranged]that its track battery is at the end adjacent said staggered jointaaprotective relay con nected across the rails of. thetrack between saidstaggered joints, and aback contactof said protective relay connected inseries with said track relay.

11. In a railway'signal system, the cornbination with a railwaytrack'divided into blocks by insulated joints, other insulated 100"joints-for dividing one of said blocks i'nto" 1 track sectlonswhichother jolnts are arranged inFstaggered-relation so as to permit. asingle axle with its wheels tooccupy one rail ofeach twosuccessiVetracksections, a track circuit for each section ofsald one block eachincluding the usual trackbattery anda'trackrelay, '1 one of saidtrackclrcults being arranged to have its track relay located at theendlo'fsaid; staggered joints and'the otherof said track circuits being soarranged that-its track battery is at" the end adjacent said staggered joints, and a protective relay connected across I the rails of the trackbetween said staggered joints, and a back contact'o't said protective Vrelay connected in 'series with na'track bat terya t 12. In a railwaysignalsystern the blocks by 1 {insulated joints,. other insulatedjoint-sjfor dividing one of said: blocks into track sectionsiwhichotherjointsare ar nationwith :a railway track divided into;-

ranged in'staggeredrelation so as to permit 1 nected in series with saidad acent track othertrack: circuit beingarranged to have its trackbattery located adjacent said staggered joints, and two back contacts onsaid protectivev relay one connected in series with said adjacent trackbattery and the other conrelay, whereby if a train occupies the trackbetween said staggered joints said protective relay is energized andboth of said track, circuits are opened.

13. In a railway signaling system; the combination with a railway trackdivided'into sections by insulated joints; a track circuit of the usualtype including a source of energy, the track rails of a section and atrack relay connected in series for each of two successive sections byinsulated joints, a track circuit of the usual type including arsourceof energy, the track rails of a section and. a track relay connected inseries, for each of two successive track sections; and means including aprotective relay for opening said two track circuits 7 when saidinsulated joints are bridged by a train.

15. In a railway signaling system of the -absolutepermissive-block typein which it is: dangerous for a line relay to be momentarily energizedduet -to the passage of a train; the

combination. with. a-railway track divided into sections by insulatedjoints; a track .cir-

cuit otthe usual type including a sourceof energy, theitrack rails of asection and a track relay connected in series, for each of' twosuccessive track sections; and means for opening the two track circuitsfor the two successive sections when a trainbridges said I insulatedjoints.

16. In a railway signaling system of the absolute-permissive-block typein which it is dangerous for a line relay to be momentarily energizeddue to the passage of a train, the combination with a railway trackdivided into sections by insulated joints, a track circuit of the usualtype for each of two successive sections including a source of energyand a track relay, and means including a protective relay controlledin amanner to open saidtwo track circuits when a train bridges the track andone of said insulated joints.

1?. In a railway signal system, the'combination with a railway trackdivided into blocks by insulated joints, other insulated joints fordividing one of said blocks into track sections, a track circuit foreach section of said-one block eachtrack circuit including the usualtrack battery and a track relay, and 1' a protective relay connectedacross'thesrails of the track to be energized when oneof said: otherinsulated joints ,arebridged, and two,- back contacts on saidprotectiverelay: onecontained in one of said track circuits and the. othercontained in the other ofrsaid-track;

circuits. i V

18. In a;railway signal system, the combi-,

nation with a railway track divided into blocks by insulated joints,other insulated joints for dividing one ofsaid blocks into tracksections, a track circuit-for each section o'tsaid one blockeachincluding the usual track battery and a track relay, one of said trackcircuits being arranged to'have its track.

relay located at the end adjacent said other joints and the other ofsaid track circuits b8?- ing so a ranged that the track; batteryis at;

the end adjacent said other joints, a protective relay connected acrossthe railsof-the track to be energized when said other: joints arebridged by a gassing train, and aback contact of said protective relay:connected in one ofsaid track circuits. 7

19. Insarailwaysignal system, the combi-i nation with a railway trackdivided into two 7 adjacent track sections by staggered insulatingrjoints, aftrack' circuit=for each of said; sections for governingHLWQYSICIQ SIgIHLI, anda protective relayincluding a=battery .in-,se- Iries therewith for' governing said wayside si 'nal connected across therails between Said:

staggered I insulating joints, whereby said: protective relay isenergized so long as a;car

axle. andfits associatedpwheels bridge; the v sa d; staggeredlnsulatlngi rails between joints.v

In testimony whereofI .aifix my signature}:-

HEBMON-"Pi. OBERL;

